In recent years, hybrid cells which can produce human antibody have been made by two methods, which can be classified basically as follows:
(1) Producing hybrid cells by combining human antibody-producing cells with a myeloma cell line originally derived from mice, rats, or other rodents.
(2) Producing hybrid cells using a human myeloma cell line.
In the interspecific hybrid cells produced according to the first method, human chromosomes rapidly disappear; it is therefore extremely difficult to obtain stable human antibody-producing hybrid cell lines. In the second method, human myeloma cell lines die immediately in a polyethylene glycol solution, which is the most easily employed cell fusion agent, and thus, no hybrid cell line can be efficiently obtained.